When using an axial piston pump in an open circuit cavitation problems arise in the region of the suction opening of the axial piston engine if care is not taken to provide a satisfactory amount of hydraulic medium to be taken in. It is known to solve this problem by making the suction opening in the connecting piece of the axial piston pump larger than the output opening on the pressure side. With this arrangement the direction of displacement of the axial piston machine is predetermined, and it is therefore not possible to change the direction of displacement. In order to be able to use such an axial piston pump for both directions of displacement the art has gone over to providing two mirror image connecting pieces for the axial piston pump. By interchanging the connecting pieces such an axial piston pump can be adapted to the desired direction of displacement. An arrangement of this kind is very inconvenient, not only because two connecting pieces have to be provided, but also because the connecting piece not being used requires a storage space so that it is available when required.